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Discussion Starter #1
I have a 1978 Ford bronco. I recently had the replace the timing chain and gears. Everything is lined up and it starts. However, as soon as I start it, it dies. If I jump the starter solenoid it will stay running. I did change the ignition switch, engine control module, and starter solenoid. The bronco ran fine before the nylon cam sprocket broke. What am I chasing here?
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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It sounds like an ignition problem. On older vehicles, when you turn the key to start, it sends power to turn on the solenoid. When the solenoid turns on it supplies power to the starter. It also supplies temporary 12v power to the ignition system.

When you turn the key back to run, the solenoid tutns off, cutting power to the starter & that temporary power to the ignition.

Your symptoms sound like there is a problem getting power to the ignition system when the key is in the run position. The temp feed from the solenoid bypasses the regular feed & will allow it to fire while cranking.

You could test the theory by pulling the wire from the small I terminal on the solenoid & connecting the wire to hot. Don't run it for long like this. If that works then you're looking to see why normal run power is missing.
 

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The troublehsooting guide for this issue would also have you check/replace the pickup in the distributor and then look at the wiring going to the coil. IE if you have an aftermarket tach pay special attention to those wires.
I have had a wire chaffed and create the same issue; I also have had the pick up in the dizzy do this as well (2 times). Fortunently you can change that out with it still in engine.
 

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Discussion Starter #4
El kabong,
I have already established that. I was trying to see what else to check. Or how to see what wires part to check.
I'm completely confused with this problem. Thanks for the help.
 

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Discussion Starter #5
CrazyBEONCOguy,
When I replaced the chain and sprockets. I also changed the distributor. I guess I forgot to mention that. So I actually replace the ignition switch, icm, stater solenoid, distributor and coil. I really can't imagine what the problem would be since it started and ran before changing all this. I guess I could have got a faulty part.
 

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Discussion Starter #6
The troublehsooting guide for this issue would also have you check/replace the pickup in the distributor and then look at the wiring going to the coil. IE if you have an aftermarket tach pay special attention to those wires.
I have had a wire chaffed and create the same issue; I also have had the pick up in the dizzy do this as well (2 times). Fortunently you can change that out with it still in engine.
When I replaced the chain and sprockets. I also changed the distributor. I guess I forgot to mention that. So I actually replace the ignition switch, icm, stater solenoid, distributor and coil. I really can't imagine what the problem would be since it started and ran before changing all this. I guess I could have got a faulty part.
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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7,632 Posts
El kabong,
I have already established that. I was trying to see what else to check. Or how to see what wires part to check.
I'm completely confused with this problem. Thanks for the help.
Just to clarify, you disconnected the I wire from the solenoid, hooked it up to 12v, & the truck will start & run until you disconnect the I wire from 12v, correct?
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
Joined
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7,632 Posts
It looks like there is a red/green resistor wire that runs from the ignition switch to a junction where the brown wire from the solenoid I terminal joins it. Then a red/green wire from there to the positive side of the coil. Since the truck runs on the wire from the solenoid it looks like your trouble should be in the resistor wire, where it connects to the brown wire, where it connects to the ignition switch, or the ignition switch itself.

I'd grab a multimeter & start testing along the way to see where power disappears headed to the coil. Be aware that everything after the resistor wire will read at lower than 12v (9v iIrc). I suppose it's possible that a failing coil might work on the full 12v from the solenoid, but not have enough kick at 9v from the resistor. But your testing will tell. If you've got voltage at the coil with the key in the Run position it might point to a weak coil.

 

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Discussion Starter #10
It looks like there is a red/green resistor wire that runs from the ignition switch to a junction where the brown wire from the solenoid I terminal joins it. Then a red/green wire from there to the positive side of the coil. Since the truck runs on the wire from the solenoid it looks like your trouble should be in the resistor wire, where it connects to the brown wire, where it connects to the ignition switch, or the ignition switch itself.

I'd grab a multimeter & start testing along the way to see where power disappears headed to the coil. Be aware that everything after the resistor wire will read at lower than 12v (9v iIrc). I suppose it's possible that a failing coil might work on the full 12v from the solenoid, but not have enough kick at 9v from the resistor. But your testing will tell. If you've got voltage at the coil with the key in the Run position it might point to a weak coil.

I replaced the ignition switch. I have already taken most of the dash out. I will grab a multi meter tonight and start checking things. I will come back with the number and we can go from there. I am terrible with electrical but I will give it a shot. If I have a bad resister wire where can I find one of those? Does it splice like any other wire? can you tell me a little more about that process?
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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7,632 Posts
Whenever I've replaced a resistor wire I've always just used regular wire with a ballast resistor in the middle. Looking around a little, it looks like the common ones are are a higher ohm rating than the 1.05-1.15 ohm that the diagram shows. With a little digging you might find a correct one.

You mentioned replacing the ignition switch. You might want to try backprobing the plug to that switch to see if you have a good conection at the switch.
 

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Discussion Starter #12
I really appreciate all the help. I didn't get around to it tonight and looks like I won't until this weekend.
 
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